The conversion of either carbon monoxide or carbon dioxide into derivatives with a C—C bond is an important first step in developing technology for producing organic chemicals from these C1 feedstocks. Due to its low reactivity, carbon dioxide poses a particular challenge, yet an important one, to achieve efficient utilization of many carbon feedstocks in large-scale fuel or commodity chemical production. An emphasis on carbon dioxide utilization has inspired development of CO2-to-methanol technologies.
One approach uses promoted Cu/ZnO heterogeneous catalyst systems similar to current commercial methanol technologies. The reaction proceeds according to Equation (1) below:

Relevant to an understanding of such CO2 hydrogenation catalysis is the water-gas-shift (WGS) reaction according to Equation (2) below:

The WGS reaction is reversible and is catalyzed by many different transition metals. It is used on an industrial scale for hydrogen generation in ammonia and methanol synthesis. Such practice uses metal oxide catalysts in a two-step, high (T>350° C.) and low (210-240° C.) temperature, process. Homogeneous catalysts for the WGS reaction show significant activity at much lower temperatures (60-160° C.).
But it is the opposite reaction, referred to as the “reverse water-gas-shift” (RWGS) reaction, that is germane to CO2 hydrogenation. The RWGS reaction is considered the first step of the process depicted in Equation (1), i.e., the conversion of CO2 to CO. The CO is then hydrogenated to form methanol.
The CO2-to-methanol process according to Equation (1) accomplishes two chemical steps in a single reactor, with a single catalyst system: RWGS and methanol synthesis. The term “tandem catalysis” has been coined to describe such processes, and examples where both chemical steps are catalyzed by the same catalyst system are referred to as “concurrent tandem cataylsis.”
In one aspect, the present invention aims to execute three chemical steps in a single unit operation and, thus, might be referred to as “double-tandem” catalysis: RWGS reaction; methanol synthesis; and methanol homologation to ethanol, all in a single step with the stoichiometry described in Equation (4) below:

Demanding aspects of “double-tandem” catalysis are that all three reactions should occur at generally the same conditions of temperature and pressure, the products of one reaction should be acceptable as reactants for the next (twice), and the promoters or co-catalysts for one reaction should not be poisons (or ideally, they would also be activators) for the subsequent reactions.
JP 3,614,449 B2 (Tominaga et al., 2004) discloses the conversion of carbon dioxide to ethanol using a ruthenium-cobalt-iodide catalyst system in a pyrrolidone or imidazolidinone solvent. JP '449, however, neither claims nor observes concurrent conversion of carbon monoxide feedstock. JP '449 also does not disclose using a molten salt as the reaction solvent.
In another aspect, the present invention aims to produce methanol and ethanol by reacting carbon monoxide with water.
The present invention addresses these as well as other objects, which will become apparent from the following description and the appending claims.